Device and method for attaching a member in replacement of part of a set of teeth

ABSTRACT

A device for attaching a member that replaces a part of a set of teeth, wherein the device has a pin to be implanted in a jawbone and a coupling pin with a ball-and-socket joint disposed between the coupling pin and the implantation pin. The ball and/or the socket of the joint is made of a memory material. The memory position is such that at body temperature pivotal motion of the ball-and-socket joint can simply be brought into a desired position. Thus, the coupling pin can be brought into any desired position, virtually independently of the orientation of the implantation pin in the jaw, so that the dental-replacement member can be fitted readily without any tension arising therein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for attaching a member in replacementof part of a set of teeth, comprising: a hollow pin to be implanted injawbone and a coupling pin to be rigidly attached to the implantationpin by means of a ball-and-socket joint.

2. Descripton of the Prior Art

Such a device is disclosed in the European Patent Application 0,263,274.It is designed for anchoring in the mouth of, for instance, a humanbeing, a dental-replacement member such as a crown, bridge or prosthesisin replacement of one or more teeth and/or molars.

A dental-replacement member is applied by first implanting one or morehollow pins in the patient's jawbone. After a certain time, the couplingpin for coupling the dental-replacement member is attached thereto. Theexact position where such an implantation pin is implanted, as well asthe orientation of the implantation pin relative to the bone, mainlydepends on the constitution of the bone in question: it will be clearthat it is desirable for the implantation pin to be implanted in a boneportion that satisfies certain minimum requirements with respect tothickness and solidity. It may thus happen that the orientation of theimplantation pin relative to the bone deviates from the desiredorientation relative to the dental-replacement member.

Particularly when a plurality of implantation pins are used to attachone and the same dental-replacement member, it is desirable for thecoupling pins of these implantation pins to be oriented parallel to eachother. However, in practice it is almost impossible to attach theimplantation pins in parallel orientation: some degree ofnon-parallellism is nearly always inevitable.

Therefore, in order to facilitate the placing of the dental-replacementmember onto the pins, and/or to allow for the setting of the orientationof the dental-replacement member with respect to the implantation pin,the coupling pin is attached to the implantation pin by means of aball-socket joint. When orienting the coupling pin with respect to theimplantation pin, the ball-socket joint is loosened; when the desiredorientation is achieved, the ball-socket joint is secured.

In the known device, the ball-socket joint is an ordinary ball-socketjoint which in itself provides only the orientation facility but not thefixation, while the above-mentioned securing of the ball-socket joint isachieved by the provision of securing means in the form of a clampingscrew. Consequently, it is necessary to provide for some passage so thata tool can reach the clamping screw. Further, in the known device thesocket of the ball-socket joint is necessarily made in two-part form,the two parts being screwed together. In order to let the socket receivethe ball, said two socket parts need to be screwed loose, and afterplacing the ball in one socket part, the other socket part, which isshaped as a housing, must be placed over the ball and screwed to thefirst socket part.

One disadvantage of this known device is that it is constructionallycomplicated, in that it comprises two screw connections: one screwconnection for the socket housing to the other socket part, and anotherscrew connection for the securing screw.

SUMMARY OF THE INVENTION

Another disadvantage of this known device is that the securing force isapplied locally, i.e. at the tip of the securing screw and at the rim ofthe socket housing, so that it is difficult to have the ball and thesocket screwed tightly together without causing them to break.

A further disadvantage of this known device is that the socket housingneeds to have a rather smooth outer surface, so that it is relativelydifficult to get a good grip thereon for screwing it onto the othersocket part without causing any damage like burrs.

It is an object of the invention to improve this known device.

More particularly, it is an object of the invention to provide a devicefor attaching a dental-replacement member, which permits steplessadjustment of the orientation of the pins protruding from the jaw, evenafter implantation, if so desired, but not at the expense of rigidity.

Further, it is an object of the invention to provide a device forattaching a dental-replacement member, which has a simple constructionand is readily attachable.

Still further, it is an object of the invention to provide a device forattaching a dental-replacement member, wherein the loosening andsecuring of the ball-socket joint does not involve turning a screw.

To that effect, the device of the type described hereinabove ischaracterized according to the invention in that at least one of thecoupling members of the ball-and-socket joint is at least partly made ofa memory material.

The memory material is provided in the ball-and-socket joint in such away that at the operating temperature thereof there is a tendencytowards a memory position, with the result that a clamping force ariseswhich fixes the ball-and-socket joint. Beyond a certain criticaltemperature, this effect does not occur and the memory material can bedeformed to make the ball-and-socket joint freely movable, whereafterthe ball-and-socket joint can be brought into any desired position,which desired position is fixed by adjusting the ball-and-socket jointto an operating temperature again.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereinafter be further explained, by way of example,by a description of preferred embodiments, with reference to theaccompanying drawings, in which:

FIG. 1 shows an elevation, partly sectional, of one embodiment of adevice according to the invention for attaching a dental-replacementmember;

FIGS. 2A-2D shows elevational views, partly sectional, of the separateparts of the embodiment shown in FIG. 1;

FIG. 3 schematically shows an example of an application of theembodiment shown in FIG. 1;

FIGS. 4A and 4B show other examples of applications of the embodimentshown in FIG. 1;

FIGS. 5A and 5B show further details of the embodiment shown in FIG. 1;

FIGS. 6A-6B shows a part of the embodiment shown in FIG. 1 in the memoryposition;

FIG. 7 schematically shows steps of setting a combination of a deviceaccording to the invention; and

FIG. 8 schematically shows an elevational view of a known device forattaching a dental-replacement member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

First, reference is made to FIG. 8, showing a known device 100 forattaching a dental-replacement member. The device 100 comprises an in,plantation pin 110 to be implanted in jawbone 111, the terminal end ofpin 110 being provided with an internally threaded portion 112. Screwedinto this portion 112 is a corresponding externally threaded portion 122of a coupling pin 120 to be coupled with a dental-replacement member(not shown). This figure clearly shows that the coupling pin 120 isdisposed axially in alignment with the implantation pin 110, so thatwhen the implantation pin 110 is implanted obliquely in the jawbone 111,the coupling pin 120 is also oriented obliquely relative to the jawbone111.

FIG. 1 shows a preferred embodiment of a device 1 according to theinvention in assembled condition, while FIGS. 2A-2D separately shows theseparate parts of this preferred embodiment: an implantation pin 10, atransmucosal member 20 and a coupling pin 30, which last is shown twicein FIGS. 2A, i.e. two mutually perpendicular side elevational views. Theimplantation pin 10 is intended for implantation in jawbone 11 (FIG. 3),and for that purpose is made of a material suitable for implantation,for instance titanium (grade 2) or TiAl₄ V₆ (grade 5), and at itsexternal surface is provided with a screw thread 12. Generally, theimplantation pin 10 is provided externally with a coating of artificialbone, for instance calcium hydroxyl apatite. Generally, the implantationpin 10 has a hollow cylindrical form which is also provided internallywith a thread 13, and is open at one end for receiving a correspondinglythreaded portion 22 of the transmucosal member 20.

The function of the transmucosal part 20 is to bridge the layer of gums21 (FIG. 3) on the jawbone 11 and for that purpose it is made of asuitable material therefor, such as TiAl₄ V₆.

The coupling pin 30 is intended for coupling with a dental-replacementmember 40 (FIG. 3), and for that purpose has a generally slightlytapering cylindrical shape, in which there may be providedcircumferential grooves 31 whose function will be further explained. Aswill appear more in particular from the side elevation of FIGS. 2A-2D,the coupling pin 30 may be flattened on one side in the longitudinaldirection, which is advantageous in particular when a member inreplacement of a tooth is being attached, since a tooth has relativelysmall transverse dimensions and is somewhat concave on the inside,while, further, rotation of the dental-replacement member is preventedby virtue of the flattened portion and the corresponding recess in thedental-replacement member.

At its wider end 32, the coupling pin 30 is provided with a fixingportion 33 which is substantially shaped as a segment of a sphere. Thepurpose of spherical fixing portion 33 is to affix the coupling pin 30in its operating position to the transmucosal member 20 at the operatingtemperature, which member 20 is provided for that purpose with acorresponding spherical hollow 23. During the setting of the couplingpin 30 relative to the implantation pin 10, the spherical fixing portion33 and the corresponding spherical hollow 23 function as aball-and-socket joint.

As shown in more detail in FIG. 5A, both the fixing portion 33 and thehollow 23 corresponding therewith extend beyond the diameter 34 of thespherical body, so that once the fixing portion 33 is disposed in thehollow 23, it can in principle be removed therefrom only by deforming atleast one of the abovementioned parts, which will generally requireconsiderable force. Further, the fixing portion 33 extends beyond thehollow 23, so that the longitudinal axis of the coupling pin 30 and thelongitudinal axis of the implantation pin 10 can be displaced relativeto each other through a certain angle, for instance at least 15°, as isillustrated more particularly in FIG. 5B. Further, it will be clear thatthe coupling pin 30 can be rotated 360° about its longitudinal axisrelative to the implantation pin 10, and that the longitudinal axis ofthe coupling pin 30, displaced through the abovementioned angle relativeto the longitudinal axis of the implantation pin 10, can be displacedthrough 360° relative to the longitudinal axis of the implantation pin10 through a precessional movement.

The fixing portion 33 is divided into at least two parts 36 by at leastone axially extending slot 35. Preferably, and as shown, there areprovided two of such slots 35₁ and 35₂, perpendicular to each other, soas to divide the fixing portion 33 into four substantially equalquarters 36. The provision of more slots somewhat reduces the strengthof the spherical portion 33; if only one slot is provided to divide thespherical portion 33 into two sphere parts, there is a chance that thiswill not permit sufficiently smooth adjustment. It is also possible, forinstance, to provide three slots extending from the side only as far asthe centreline to thereby divide the spherical portion 33 into threesphere parts, but this is more complicated from the point of view ofmanufacturing technique, and hence more expensive.

The fixing portion 33, at least the part thereof where the quarters 36are joined together, consists of a memory material, with the parts 36being disposed relatively far apart in the memory position (see FIGS.6A-6B). The memory material is of such a type that the memory propertiesof the material in question are achieved at least in a temperature rangethat includes the normal body temperature of the carrier, which is about37° C. in the human body. Normal operating temperatures in the mouth ofthe human body will not go beyond the range of 0° C. to 80° C. As in thememory materials known to date the memory effect occurs above a certaincritical temperature, preferably a memory material is used with acritical temperature that is sufficiently lower than 37° C. andpreferably about 0° C. A suitable material is known under the name ofnitinol.

It is observed that although within the framework of the presentinvention it is possible for only a part of the coupling pin 30 toconsist of memory material, for instance the spherical portion 33, whilethe remaining portion may consist of a different, cheaper material, itis easier from the point of view of manufacturing technique to make theentire coupling pin 30 of memory material.

With reference to FIG. 3, now the attachment of a dental-replacementmember 40 using a device 1 according to the invention will be described.For the sake of clarity, adjacent dental elements are not shown.

In a first session--that is, obviously, after any original dentalelements and/or root parts have been removed, and, if so desired, a holehas been provided in the jawbone 11 --an implantation pin 10 is screwedinto the jawbone 11, whereby the orientation of the implantation pin 10is not critical.

In the practical example shown in FIG. 3, two of such implantation pins10 have been implanted.

After the implantation pin 10 has sufficiently grown into the jawbone11, i.e. that growth of the jawbone 11 has led to sufficient anchoringof the implantation pin 10, the combination of the transmucosal member20 and the coupling pin 30 is screwed into the implantation pin 10.Preferably, each coupling pin 30 is positioned relative to thecorresponding transmucosal member 20 in such a way, that after thescrewing step each coupling pin 30 has a desired orientation relative tothe jawbone 11. FIG. 3 shows that the two coupling pins 30 are orientedparallel to each other, in spite of the fact that the correspondingimplantation pins 10 deviate considerably from this orientation. FIG. 4Ashows a practical example in which three devices 1 according to theinvention have been employed, with the three coupling pins 30 beingoriented parallel to each other. FIG. 4B shows a practical example inwhich a device 1 is used for attaching separate dental elements.

After the gums have healed sufficiently, the dental-replacement member40 can be mounted on the coupling pin(s) 30 by fitting thedental-replacement member 40 over the coupling pin(s) 30. For thatpurpose, the dental-replacement member 40 is provided with recesses 41corresponding with the coupling pins 30. Securement of thedental-replacement member 40 relative to the coupling pin 30 can beaccomplished by a click-fit connection, by depositing cement in therecesses 41 or by screwing one or more securing nuts (not shown for thesake of simplicity) in the dental-replacement member 40, which securingnuts extend into said circumferential grooves 31. This last possibilityis particularly advantageous in the case of a comprehensivedental-replacement member 40, such as a bridge, in that, if so desired,the member 40 can be removed and re-placed again in simple mannerwithout risk of damage, while the dental-replacement member 40 is stillprevented from being "loose" in use.

It is noted that in general the manufacturer supplies to the dentist ordental surgeon the combination of coupling pin 30 and transmucosalmember 20 as an assembly. The manufacture of such a combination canadvantageously be realized in the following manner. Using means that areknown per se, a transmucosal member 20 is manufactured from a suitablematerial, for instance TiAl₄ V₆, with the transmucosal member 20 beingprovided, among other things, with a spherical recess 23, as describedabove. Likewise using known means, a coupling pin 30 is manufactured inits entirety from a memory material, for instance nitinol, with acritical temperature of about 0° C., the coupling pin 30 being provided,among other things, with a spherical fixing portion 33. The dimensionsof the spherical fixing portion 33 are substantially equal to, possiblyslightly smaller than, the dimensions of the spherical recess 23. In thespherical fixing portion 33 two axial slots 35 are provided to dividethe spherical fixing portion 33 into four quarters 36, as describedabove. Using a suitable tool, these quarters 36 are moved apart at atemperature above the critical temperature until the position shown inFIGS. 6A-6B has been reached, where the external dimensions of thespherical fixing portion 33 are greater than the correspondingdimensions of the spherical recess 23.

This position shown in FIGS. 6A-6B is the so-called memory position ofthe spherical fixing portion 33. This means that at a temperature abovethe critical temperature, the spherical fixing portion 33 will at alltimes attempt to assume the position shown in FIG. 6A-6B. At atemperature below the critical temperature, this effect does not occur.This is made use of in the manufacture of the abovementioned combinationby cooling the spherical fixing portion 33 to a temperature below thecritical temperature and pinching the quarters 36 inwardly, whereby aplastics deformation can occur, and then introducing the sphericalfixing portion 33 into the spherical recess 23 of the transmucosalmember 20. In this condition the spherical fixing portion 33 is freelymovable within the spherical recess 23, and the combination of thespherical fixing portion 33 and the spherical recess 23 functions as aball-and-socket joint. In this condition, therefore, the coupling pin 30can be brought into a desired orientation relative to the transmucosalmember 20.

Then the temperature of the spherical fixing portion 33 is raised abovethe critical temperature. Under the influence of the memory effect, thequarters 36 will attempt to assume their memory position again, but areprevented from doing so by the wall of the spherical recess 23, so thatthe quarters 36 will push against the wall of the spherical recess 23with a considerable force. Thus, any movement of the spherical fixingportion 33 relative to the spherical recess 23 is prevented, so that theorientation of the coupling pin 30 relative to the transmucosal member20 is fixed in the position set, at least in the case of such forces asmay generally be exerted within the mouth. The fixing power can beincreased by forming the spherical fixing portion 33 and/or thespherical recess 23 with a slightly rough surface.

It is observed that the combination of the coupling pin 30 and thetransmucosal member 20 can thus be regarded as one integral part attemperatures above the critical temperature, and hence at least at suchoperating temperatures as may occur in the mouth. Thus, the inventionmakes it possible to implant an implantation pin in the jawbone in anorientation that is suitable for implantation, and to attach thereto astandard integral part comprising a coupling pin, while the coupling pinstill has an orientation that is suitable for coupling with thedental-replacement member.

When setting the coupling pin 30 relative to the implantation pin 10,the dentist can work "by eye", but greater accuracy is achieved by meansof the procedure to be described hereinafter with reference to FIG. 7,which is particularly preferable if a dental-replacement member is to beattached by means of a plurality of anchoring elements.

After implantation and ingrowth of the implantation pins 10, the gums 21are opened locally and an auxiliary pin 50 is screwed into eachimplantation pin 10 by means of a comparatively long screw 51. Then,using an impression mass 52 which is known per se, an impression(negative) is made of the jaw and the auxiliary pins 50 protrudingtherefrom, as well as of any original dental elements (see FIG. 7A).This impression mass 52 is applied by means of a so-called "impressionspoon" which is accessible from the side facing away from the jaw forunscrewing the screw 51, so that the impression mass 52 with theauxiliary pins 50 disposed therein can be removed (see FIG. 7B).Optionally, a temporary transmucosal member can then be attached to theimplantation pins 10 to prevent closing of the gums.

In a preferably separate laboratory, an implantation pin 10 is attachedagain to the auxiliary pins 50 stuck in the impression mass by means ofa separate screw 51' (see FIG. 7C), and of the assembly an impression(positive) 54 is made (see FIG. 7D). This positive impression 54 (seeFIG. 7E) is a replica of the relevant situation in the mouth, includingthe implantation pins 10.

A respective combination of a transmucosal member 20 and a coupling pin30 is mounted on these implantation pins, whereafter, after coolingappropriately, the coupling pins 30 are brought into a desiredorientation and are secured in that desired orientation by heating (seeFIG. 7F).

Then, recesses are provided in a dental-replacement member 40, whichrecesses correspond with the orientation of the coupling pins 30 of thepositive impression 54. This may for instance be realized by moulding awax model of the dental-replacement member 40 on the positive impression54, and forming the dental-replacement member proper from the wax modelby means of the lost-wax method, as is known per se.

The dental-replacement member 40 so prepared and the correspondingcombinations of transmucosal member 20 and coupling pin 30 (see FIG. 7G)are fitted in the patient's mouth by the dentist, the dental-replacementmember 40 generally fitting readily on the coupling pins 30 withoutfriction or tension, when the abovementioned combinations oftransmucosal member 20 and coupling pin 30 have been attached to thecorresponding implantation pins 10.

Optionally, however, it is possible for the dentist to suspend the fixedposition by locally cooling the coupling pins 30 and to fit thedental-replacement member over the coupling pins 30, whereby the pins 30will orient themselves in the recesses 41 of the dental-replacementmember. By reheating the coupling pins 30 again to a temperature abovethe critical temperature, the position of the coupling pins 30 thusadjusted to the dental-replacement member is maintained in the mouth. Itwill be clear that the surrounding parts, such as gums, are protectedagainst the low temperature, for instance by means of a so-calledcofferdam, as is known per se.

It will be clear that the invention also relates to embodiments in whichthe ball cup of the ball-and-socket joint consists of a memory materialand in the memory position exerts an inwardly directed clamping force onthe ball. In a possible embodiment, the transmucosal member 20 is madeof memory material. However, since generally at least one slot isdesired to provide clamping portions equivalent to the clamping portions36, while, at the same time, such a slot is less desirable inconjunction with gums, the embodiment discussed above with reference tothe drawing is preferred.

It will be clear to anyone skilled in the art that it is possible tochange or modify the embodiment shown of the device according to theinvention, without departing from the concept of the invention or thescope of protection.

We claim:
 1. A device for attaching a member in replacement of part of a set of teeth, comprising:a hollow implantation pin to be implanted in a jawbone; and a coupling pin adapted to be rigidly attached to the hollow implantation pin by means of and further comprises a ball-and-socket joint; wherein: a coupling part of the ball-and-socket joint is at least partly made of a memory material to prevent pivotal motion of the ball-and-socket joint at an operating temperature.
 2. A device according to claim 1, wherein the coupling pin comprises at one end a fixing portion substantially shaped as a segment of a sphere, which segment of a sphere is entirely made of memory material.
 3. A device according to claim 2, wherein the coupling pin is entirely made of memory material.
 4. A device according to claim 1, wherein the coupling part of the ball-and-socket joint that is at least partly made of memory material is subdivided into separate clamping parts by means of slots.
 5. A device according to claim 4, wherein two slots are provided in said coupling part in substantially perpendicular relation relative to each other.
 6. A device according to claim 1, wherein the surface of said coupling part of the ball-and-socket joint is slightly roughened.
 7. A device according to claim 1, wherein said ball-and-socket joint further comprises a transmucosal member, said transmucosal member being suitable at one end thereof for attachment to the hollow implantation pin and at its other end comprises a second coupling part of the ball-and-socket joint.
 8. A device according to claim 1, wherein a critical temperature of the memory material is lower than 37° C.
 9. A device according to claim 8, wherein the critical temperature of the memory material is about 0° C.
 10. A device according to claim 1, wherein the memory material is nitinol.
 11. A coupling pin for attaching a replacement part of a set of teeth to an implantation pin, said coupling pin comprising a coupling part of a ball-and-socket joint at an end of said pin wherein said coupling part is at least partly made of a memory material.
 12. A coupling pin according to claim 11, wherein the coupling pin comprises at one end a fixing portion, substantially shaped as a segment of a sphere, said segment of a sphere being entirely made of memory material.
 13. A coupling pin according to claim 12, wherein the coupling pin is entirely made of memory material.
 14. A coupling pin according to claim 11, wherein the coupling part of the ball-and socket joint is subdivided into separate clamping parts by slots.
 15. A coupling pin according to claim 14, wherein two slots are provided in said coupling part in substantially perpendicular relation to each other.
 16. A coupling pin according to claim 11 further comprising a transmucosal member, which transmucosal member is suitable at one end thereof for attachment to the implantation pin and at its other end comprises a coupling part of said ball-and-socket joint.
 17. A transmucosal member for attaching a replacement part of a set of teeth to an implantation pin, said transmucosal member comprising a first end and a second end, said first end comprising a means for attaching the transmucosal member to the implantation pin and said second end comprising a coupling part of a ball-and-socket joint, wherein said coupling part is at least partly made of memory material.
 18. A transmucosal member according to claim 17 further comprising a coupling pin, which coupling pin is suitable at one end thereof for attachment to the replacement member and at its other end comprises a coupling part of said ball-and-socket joint.
 19. A method for attaching a member in replacement of part of a set of teeth, in which a coupling pin is attached, to the member by means of a corresponding recess in the member and the coupling pin is further attached to a ball-and-socket joint which in turn, is attached to an implantation pin implanted in a jawbone, wherein at least one of the coupling parts of the ball-and-socket joint is made of a memory material, said method comprising the steps of:cooling at least the part of the ball-and-socket joint that is made of memory material to a temperature below a critical temperature to make the ball-and-socket joint pivotable; positioning the ball-and-socket joint so as to bring the coupling pin into a desired orientation relative to the implantation pin; and heating at least the part of the ball-and-socket joint that is made of memory material to a temperature above the critical temperature so as to fix the desired position of the ball-and-socket joint.
 20. A method according to claim 19, wherein the steps of cooling, positioning and heating are carried out after the coupling pin has been attached to the implantation pin. 